Boiler MACT Compliance

Particulate Capture in an Electrostatic Precipitator


THE RPOBLEM

The ESP of the city of Hamilton, OH Municipal Electric Plant

Fig. 1. The ESP of the city of Hamilton, OH Municipal Electric Plant

The city of Hamilton, OH Municipal Electric Plant (Hamilton), operates a pulverized coal fired boiler (No. 8) subject to the boiler Maximum Achievable Control Technology (MACT) standards issued by the US EPA. EQ Engineers, LLC (EQE) has been employed by Hamilton to study and evaluate options for achieving MACT standards on a consistent basis as part of an overall compliance plan. The current configuration of the ductwork leading into the Electrostatic Precipitator (ESP) is not producing a uniform flow pattern. It is believed that the variation in flow velocity across the face is contributing to particulate matter (PM) emissions that exceed the MACT standards.


THE PROJECT

The CFD model of ESP

Fig. 2. The CFD model of ESP

In reality, the ESP has low efficiency to capture the particulate matters which lead into exceeding the emission standards. There are many possibilities to cause this issue. Mainly, they are falling into two groups: one is the rapper design, and the other one is the flow turbulences. The company believes that the design of the rappers is well suited for the type and size of particles carried by the gas stream.  Therefore, the flow behavior inside the ESP needs to be investigated.  Turbulent flow can result in low efficiency of the ESP particle capture. The turbulent flow can be caused by the particle load or the configuration of the inlet duct, ESP and outlet duct. The objective of this project is to determine the most dominant cause of the turbulent flow.


THE RESULTS

Velocity Streamlines inside the ESP

Fig. 3. Velocity Streamlines inside the ESP

The configuration of the inlet duct, especially the screen, causes the turbulence eddies that lead to poor particle capture efficiency.  Results of the CFD simulations have enabled us to analyze particulate matters distributions and flow field inside the ESP. The RMS (root-mean-square) velocity has been monitored on some key planes. 

Sponsor: EQ Engineers, LLC

Boiler MACT Compliance project flyer

Boiler MACT Compliance Project Flyer